Cumulative impact assessment (CIA) is the process of assessing a proposed action’s cumulative environmental effects in the context of other past, present, and future actions, regardless of who undertakes such other actions (CEQ, 1978). The National Environmental Policy Act (NEPA) is generally acknowledged as the first legislative impetus behind CIA. It established a framework under which federal agencies are required to consider project-specific and cumulative environmental impacts of proposed projects prior to their undertaking. NEPA applies to federal actions, but many projects occur as a result of non-federal actions and are subject to formal environmental review administered by state governments. In contrast to the rich literature on federal efforts, little is known about state environmental review and CIA policies and practices...